Evaluation and obstacle factors of coordination development of regional water-energy-food-ecology system under green development: a case study of Yangtze River Economic Belt, China

The interaction between regional water, energy, food and ecology systems has the characteristics of high correlation and complexity. In-depth study of the relationship between the four systems under green development is greatly significant for regional sustainable development. In this study, pressure-state-response (PSR) model was firstly innovatively introduced to analyze the internal coupling mechanism of water-energy-food-ecology (WEFE) system. Then an evaluation index system for the coupling coordination development of WEFE system was constructed by taking water, energy, food and ecology subsystems as the criterion layer. Finally, the coupling coordination degree (CCD) model was used to analyze the coupling coordination development level of the nine provinces and two cities along the Yangtze River Economic Belt (YREB) from 2008 to 2019. And obstacle degree model was adopted to explore the main factors affecting the coupling coordination development of WEFE system. The results showed that the development level of the WEFE system in the YREB was far-reaching influenced by the development of energy subsystem on the one hand, and also by food subsystem on the other hand. From the perspective of time dimension, the coupling coordination development level of WEFE system in Shanghai presented a gradual upward trend with a state of intermediate coordination, and those in some provinces such as Jiangsu have undergone a brief jumping change from near coordination to primary coordination, while those in some provinces such as Anhui fluctuated up and down from 2008 to 2019. As for the YREB, it always remained in the state of the primary coordination with unobvious upward trend, which presented the characteristic of "lower reaches > upper reaches > middle reaches". In terms of the space dimension, the CCD values of WEF system in the YREB showed an obvious concave distribution pattern of "higher in the east and west, but lower in the middle" during the study period. Proportion of environmental protection investment and food production per unit area were the primary and secondary factors affecting the coupling coordination development of WEFE system in the YREB. Therefore, some recommendations should be put forward to promote green sustainable development of regional resources and environment.